A fuel tank of that kind is known for example from EP 1 196 303 B1. The fuel tank known from EP 1 196 303 includes means for venting same when refuelling the tank and in operation of the motor vehicle. The venting lines are connected in known manner by way of a collecting container to a pressure compensating line connected to an activated carbon filter.
When filling the fuel tank with fuel the gas present in the tank is displaced by the incoming flow of liquid. So that no hydrocarbons are discharged to the atmosphere in the refuelling operation, the gas volume flow which is displaced in the refuelling operation is usually discharged to the atmosphere by way of a fuel vapor filter. The gases which are produced in operation of the motor vehicle as a result of evaporation of the fuel are also discharged to the atmosphere in a cleaned form by way of the fuel vapor filter.
The activated carbon in the fuel vapor filter may not be wetted with liquid hydrocarbons, such wetting would detrimentally affect the adsorptive properties of the activated carbon. For that reason it is known for collecting containers or beading-out containers to be disposed upstream of the fuel vapor filter in the venting lines. Any condensate which is produced as well as entrained liquid hydrocarbon particles are deposited out in the collecting container and added to the delivery volume of the fuel tank again in a suitable fashion.
Collecting containers of that kind are arranged in part outside the fuel tank and in part within it.
To avoid potential emission and leakage points, for example EP 1 196 303 proposes arranging such a collecting container within the fuel tank so that it is possible to dispense with the arrangement of lines which communicate the internal space of the fuel tank with the collecting container.
A further advantage of a collecting container which is disposed within the fuel tank is that it cannot tear away in the event of the motor vehicle crashing as the collecting container is arranged in a protected condition within the fuel tank.
It is readily understandable that the liquid fuel which occurs in the collecting container or beading-out container must be returned again to the delivery volume of the fuel tank. That can be easily effected for example by means of the force of gravity through a drain opening provided with a valve in the collecting container.
Depending on the respective pressure conditions in the fuel tank and depending on the respective position of installation of the collecting container, emptying thereof by virtue of the effect of the force of gravity is not always effectively possible.
Therefore EP 1 196 303 B1 proposes connecting the collecting container to the suction side of a suction jet pump present in the fuel tank. The suction jet pump can be operated for example by the return flow of fuel from the engine in operation of the motor vehicle. That effectively provides that the collecting container is sucked out.
Such an arrangement however suffers from the disadvantage that additional lines have to be placed within the fuel tank, which means that in particular the assembly complication and expenditure in completing the fuel tank becomes comparatively high.